The present application generally relates to systems and methods for imaging and ablating zones in tissue. More specifically, the present application relates to using an interventional ultrasound catheter to image and ablate tissue. Tissues that may be ablated include cardiac tissue (e.g. for arrhythmias, ventricular tachycardia, atrial fibrillation and flutter, etc.), as well as non-cardiac tissue, such as afferent and efferent nerves (e.g. renal nerves, ganglionated plexi, etc.), tumors, or any other tissue which may be treated by ablation.
Tissue ablation can be used to treat various disease states. An important component of tissue ablation is identifying the target tissue and ablating that tissue, generally without significant damage to surrounding tissues that may be adjacent or collateral to the desired target tissue. As such, it is important to be able to identify both the target and surrounding tissues with an imaging modality, plan the desired lesion based on that information, and execute the planned ablation with a reduced negative impact on non-targeted tissue.
Current ablation devices rely on a number of different imaging modalities for positioning the lesion and/or identifying where the ablation device is located relative to the lesion. Imaging modalities include x-ray/fluoroscopy, electroanatomic mapping, computed tomography (CT), ultrasound, and any combinations thereof. X-ray/fluoroscopy can image the entire body, but has limited spatial resolution, limited soft tissue contrast, and exposes the patient to ionizing radiation. Electroanatomical mapping is used in cardiac ablation applications, but is limited to being a contact technology (for position information), provides no tissue information beyond the tissue surface contact, and spatial resolution is dependent on manual catheter control by the user. Spatial resolution may be improved by merging with CT images; however, the two modalities are typically acquired at different times and are often not easily available. CT images are also not available in a real-time mode. Ultrasound imaging has been used but in general only for target tissue location information provided from a secondary system that is separate from the ablation device.
Ablation devices generally use radiofrequency (RF) as an energy source and cryogenics as a cooling source. These ablation devices rely on secondary imaging modalities for positional information. They do not provide information related to tissue thickness or tissue properties that directly modulate the ablation device. They may have some limited feedback information from the tissue (such as tissue temperature), but none of the current ablation devices provide sufficient information to characterize the target and surrounding tissues and create the lesion with tissue feedback information within a single system. Combinations of the imaging modalities and the ablation devices still do not provide all the useful information to accurately place a lesion to achieve the desired result.